Radiation detectors often require interactions that convert incident radiation (e.g., neutrons, gamma rays, alpha particles, beta particles) into a measurable charge for processing and analysis. At the core of many radiation detectors is a charged particle detector. Conventional radiation detectors employ a substrate in which the radiation energy to be measured is fully deposited.
For example, FIG. 1 illustrates a conventional radiation detector 100. The conventional radiation detector 100 includes a substrate 110 coupled with a voltage source (VSOURCE) 120. The conventional radiation detector 100 is configured for full energy deposition of incident radiation 105 within the substrate 110. For example, if incident radiation 105 interacts with the substrate 110, the energy is deposited within the substrate 110, and the incident radiation 105 may cease to propagate through the substrate 110 as indicated by line 106.
In operation, the interaction of the incident radiation 105 with the substrate 110 causes charge carriers (i.e., electron-hole pairs) to be generated within the substrate 110. If an electromagnetic field is initiated by applying a voltage to the substrate 110, the charge carriers can be separated and counted. For example, electrons 108 and holes 109 may move, respectively toward the voltage leads 122, 124 of the voltage source 120. Full energy deposition of the incident radiation 105 may be significant for an accurate measurement, because the number of charge carriers created is proportional to the amount of energy in the incident radiation 105. Therefore, for the conventional radiation detector 100 to appropriately measure the total amount of energy exhibited by the incident radiation 105, the substrate 110 is configured for full energy deposition of the incident radiation 105.
FIG. 2 illustrates a radiation detector 200 according to another conventional approach to radiation detection. Radiation detector 200 includes a substrate 210 in contact with a graphene layer 211. The radiation detector 200 further includes a voltage source (VSOURCE) 220. The voltage source 220 is coupled with the substrate 210 and the graphene layer 211 in order to generate a voltage drop thereacross.
In operation, incident radiation 205 interacts with the substrate 210 as the active surface to generate charge carriers within the substrate 210. The radiation detector 200 is configured for full energy deposition of incident radiation 205 within the substrate 210. For example, if incident radiation 205 interacts with the substrate 210, the energy is fully deposited within the substrate 210, and the incident radiation 205 may cease to propagate through the substrate 210 as indicated by line 206.
If a voltage is applied by voltage source 220, the charge carriers may move toward voltage leads 222, 224 of the voltage source 220. In particular, electrons 208 may move toward the positive (+) voltage lead 222 of the voltage source 220. As a result, the electrons 208 may reach the surface of the substrate 210 and interact with the graphene layer 211. The interaction of the electrons 208 with the graphene layer 211 may cause a modification of the resistance of the graphene layer 211. The change in resistance may be determined by measuring the voltage 230 across, and the current 240 through, the graphene layer 211. The change in resistance may be proportional to the number of charge carriers generated within the substrate 210 and that come in contact with the graphene layer 211. Therefore, while the number of charge carriers is not directly counted, an accurate measurement may still be dependent upon a full change in resistance in the graphene layer 211, such that full deposition of the incident radiation 205 within the substrate 210 may still be required.
Relying on charge carrier generation and collection to determine the presence and the characteristics of the incident radiation through conventional methods may result in reduced energy resolution that may be caused by statistical variations during charge carrier collection and counting. Such statistical variation of charge carrier collection may be caused by defects, thermal effects, and semiconductor impurities in the substrate 110, 210, among other reasons.